Asus RT-AC66U_B1 H/W B2 Huawei K4505 & ZTE MF821 NOT working

I've been pulling my hair on this router as it's not working with a dongle that's even natively supported and included in listed in Merlin USB modem devices! I managed to get Dual WAN working with an Android phone only so far.

I have a locked Vodafone K4505 dongle/modem with a Vodafone PayGo SIM which just topped up. I am able to access the internet when insert the sim into Android phone connected to the router and Dual WAN is working through this phone. As soon as I connect the dongle directly to USB3 with this SIM an set correct settings it's not working as per error at the bottom.

Both modems are connecting (unlocked using different SIMs) when using on Windows 7 Pro x64 through native apps installed from dongles. Used the same APN settings were used on both mobile that connects fine and router.

I have tried setting modem vendor to Auto, reset router to factory settings and configured using Wizard but no joy...

There is a bug namely incorrect path set in a script loading modules which is looking for option.ko module in /lib/modules/kernel/usb/ which doesn't exist. The problem is that the root filing system is Read-only (more info on JFFS https://github.com/RMerl/asuswrt-merlin/wiki/User-scripts) and thus won't allow you to copy across modules, create a symlink or edit config to point to correct location.

STEPS to get it working:

1. Log into router's admin panel using admin user then go to Administration > System and set:

8, or reboot the router. When it boots up, if you have Dual WAN enabled with USB enabled as primary or backup then it'll automatically switch over to it. Be patient as it takes some time.

You can view modem communication using command 'tail -f /tmp/usb.log' or 'cat /tmp/usb.log'.

I topped up my EE account and the connection has been on for over 24h now so looking pretty stable. You may experience problems with low network coverage so to save your time buy different sim card providers, test on a phone first to see whether they connect to the internet and there is decent 3-5 bars so you don't waste your time troubleshooting problems caused by it. Also, make sure you have enough credit.

BTW - the ZTE MF821 still doesn't work and only Huawei K4505 is connecting solid after the above fix.

You might be right and it could be some invalid parameters in module load script (not sure where it's auto-loading modules) that cause the issue because it's clearly not loaded during boot or when you plug in USB modem. It starts to work fine as soon as you manually load the option.ko. I'll leave it to fix for those who are more familiar with router firmware - I am not. Thanks for pointing this out - the workaround might be more flexible without providing exact path to the module and use system defined instead (if working so test first).

You might be right and it could be some invalid parameters in module load script (not sure where it's auto-loading modules) that cause the issue because it's clearly not loaded during boot or when you plug in USB modem. It starts to work fine as soon as you manually load the option.ko. I'll leave it to fix for those who are more familiar with router firmware - I am not. Thanks for pointing this out - the workaround might be more flexible without providing exact path to the module and use system defined instead (if working so test first).